RYB Color Model LESS Mixins

ryb.less

/*
----------------------
RYB Color Model Mixins
----------------------

RYB is an artistic color model that provides somewhat better color harmonies 
(complementary, triadic &c), although not mathematically perfect since 
cannot cover the whole visible spectrum. Neither good for physical pigments encoding.

http://en.wikipedia.org/wiki/RYB_color_model
*/

/*
Color wheels
*/
@ryb-wheel: 0, 26, 52, 83, 120, 130, 141, 151, 162, 177, 190, 204, 218, 232, 246,
            261, 275, 288, 303, 317, 330, 338, 345, 352, 360;
            
@rgb-wheel: 0, 8, 17, 26, 34, 41, 48, 54, 60, 81, 103, 123, 138, 155, 171, 187,
            204, 219, 234, 251, 267, 282, 298, 329, 360;


/*
Maps a given color on the RGB wheel to Itten's RYB wheel.

@c - a color

Sets the @ryb variable as result color.
*/
.rgb2ryb(@c)
{
  .map-hue(hue(@c), @ryb-wheel);
  @ryb: hsl(@_, saturation(@c), lightness(@c), alpha(@c));
}

/*
Maps a given color on Itten's RYB wheel to RGB wheel.

@c - a color

Sets the @ryb variable as result color.
*/
.ryb2rgb(@c)
{
  .map-hue(hue(@c), @rgb-wheel);
  @rgb: hsl(@_, saturation(@c), lightness(@c), alpha(@c));
}

/*
Maps the given hue to the specified color wheel.

@hue   - a color hue
@wheel - the color wheel to be approximated

Sets the @_ variable as result hue.
*/
.map-hue(@hue, @wheel)
{
  @d: mod(15, @hue);
  @i: ceil(@hue / 15);

  @x0: extract(@wheel, @i + 1);
  @x1: extract(@wheel, min(@i + 2, 25));   // min for index boxing

  @_: @x0 + (@x1 - @x0) * max(0, @d / 15); // max is needed to coerce some edge cases
}

test-complementary.less

/*
Approximates the complementary of a given color using Itten's RYB wheel.
 
@c - a color
 
Sets the @_ variable as result color.
*/
.complementary(@c)
{
  .rgb2ryb(@c);
  .ryb2rgb(spin(@ryb, 180));
    
  @_: @rgb;
}
 
 
/*
Example of use
*/
.my-complementary
{
  background: @_;.complementary(orange);
}